UNio. 173 



in a distinct angle, but in the female very broadly rounded ; a sharp 

 ridge usually passes from the lieaks towards the posterior tip. 

 Surface considerably undulated by the lines of growth ; epidermis 

 smooth, shining, and sometimes with rays of minute wrinkles; color 

 dull greenish-yellow or light olive, usually with rays of bright, dark 

 green, especially along the upper posterior margin. Interior liluish- 

 white, with sometimes a flesh-colored tint. Cardinal teeth com- 

 pressed and oblique ; lateral tooth rather short ; cavity of the beaks 

 rather large. Length, three inches ; height of male, one and three 

 fourths inches, of female, two and one fourth inches ; breadth, one 

 and one fourth inches. 



Found in the Connecticut River and its tributaries, and in ponds 

 in Plymouth County. 



It is very difficult to fix upon characters which shall indicate this 

 shell, its variation in shape is so great. When young, it is thin and 

 beautifully radiated, and not easily distinguished from the young 

 of U. ochraceus ; and at maturity no species presents a greater con- 

 trast between the male and female than this. As found in this re- 

 gion it is quite thin, and radiated only along the posterior margin ; 

 but in the waters south of New England, it becomes larger and 

 more solid. 



Unio ochraceus. 



Fig. 74. 



Shell oblonfT, sub-ovate, inflated, thin, inequilateral, angular behind; epidermis 

 loosely wrinkled posteriorly, yellowish-green, finely radiated with olive; cardi- 

 nal teeth compressed, nearly parallel with the margin ; within salmon or rose- 

 colored. 



Unio ochraceus, Say, Nich. Encyc. (Amer. ed. 1816) iv. pi. 2, fig. 8. — Lea, Trans. Amer. 

 Phil. See. (new series) vi. 126, pi. 15, fig. 44 (animal) ; Synops. Naiad. 2.3 ; 3d ed. 

 27. — Conrad, Unionid*, 37, pi. 17, fig. 2 ; Synops. Proc. Ac. Nat. Sc. vi. 254. — 

 De Kay, Nat. Hist. New York, 193, pi 19, figs. 137, 138. — Gould, Inv. 112, fig. 74. 



Si/mjihi/notn oclmtcea, Lea, Trans. Amer. Phil. Soc. (new series) ill. 69. 



Pectimculns JJ.Hvintilis, Lister, Conch, pi. 157, fig. 12. 



Lampsilis ochracea, Stijipson, Shells of New England, 14. 



Shell transversely oblong, sub-ovate, thin, translucent, very much 

 inflated ; beaks more than one third from the front, elevated, in- 

 clined forwards and touching at the points ; hinge-margin straight, 

 ending in an angle both anteriorly and posteriorly ; anterior end 

 narrowest, compressed, especially above, rounded, and widely gaping ; 

 posterior end having its point angular in consequence of a sharply 

 angular ridge which passes from the beaks and terminates there, 



